San Mateo County, CA Building Setbacks & Zoning: Setback Rules (2026)
Key Facts
- Front setback
- 20 feet
- Rear setback
- 20 feet
- Side setback, street-facing
- 10 feet
- Side setback, interior
- 5 feet
- Applies to
- S-50 District, R-2/R-3, North Fair Oaks
- Height limit
- 28 feet, two stories
- Exception authority
- Zoning Administrator / Director of Planning
Summary
In the S-50 Combining District, layered onto R-2 (two-family) and R-3 (multi-family) parcels in unincorporated North Fair Oaks, San Mateo County requires a 20-foot front setback and a 20-foot rear setback under Zoning Regulations Sec. 8.158.050. Side setbacks are 10 feet where the side property line fronts a public or private street, and 5 feet in every other case.
8.158.010 - Regulations For "S-50" Combining District (North Fair Oaks). The following regulations shall apply in specific two-family (R-2) and multiple-family (R-3) residential districts with which the "S-50" District is combined. In the case where a requirement, standard, or provision of this Chapter conflicts with another requirement, standard, or provision in the Zoning Regulations, including this Chapter, the most limiting provision shall take precedence and govern. 8.158.050 - Building Setbacks. The minimum building setbacks shall be: Front: 20 feet. Sides: 10 feet, when the side property line fronts a public or private street; 5 feet, all other cases. Rear: 20 feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 47).
Full Breakdown
050 sets the yard minimums themselves: a 20-foot front setback, a 20-foot rear setback, a 10-foot side setback where the side property line fronts a public or private street, and 5 feet in all other side-yard cases. Those setbacks sit inside a broader S-50 development package: a minimum building site width averaging 50 feet (Sec. 020), a minimum site area of 5,000 square feet (Sec. 4 dwelling units per net acre (Sec. 45 of parcel area (Sec. 50 including patios and decks 18 inches or more above grade (Sec.
070), and a 28-foot, two-story height limit (Sec. 080). 090 layers on a daylight plane measured 20 feet up from grade and inward at 45 degrees to that 28-foot ceiling, though chimneys, pipes, mechanical equipment and antennae may extend into the daylight plane up to a maximum height of 36 feet.
Violations & Fines
Building into these setbacks or the daylight plane without approval is a zoning violation that blocks issuance of a building permit until the plans are corrected. An owner who cannot meet a yard minimum, for a residential home improvement or minor addition in an R-2, R-3 or combining district such as S-50, can ask the Zoning Administrator, the Director of Planning, for an exception under Section 8.04.050(b)(6); larger projects requiring environmental review go to the Planning Commission instead.
Frequently Asked Questions
Is the side setback always 5 feet in this district?
Do these setbacks apply everywhere in San Mateo County?
Can any part of the house extend past the setback line?
Sources & Official References
Other rules in San Mateo County
California rules heatmap·Compare San Mateo County to another location·View the California building setbacks & zoning overview
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